Die casting apparatus

ABSTRACT

Die casting apparatus of the horizontal cold chamber type operative to prevent impurities such as dross and metal foam floating on the surface of the molten metal charge in the shot sleeve from entering the die cavity. The apparatus involves the elimination of the usual vertical runner extending from the end of the shot sleeve adjacent the parting line of the dies to the die cavity, the provision of the overflow cavity above and at the end of the shot sleeve adjacent the parting line of the dies, and the provision of one or more runners extending from the lower portions of the shot sleeve and around the overflow trap whereby when the plunger is caused to move the molten metal to the parting line of the die, the dross and metal foam formed on the surface of the die is trapped in the overflow trap and only clean metal is injected into the die cavity.

United States Patent Douglas [451 Apr. 25, 1972 [54] DIE CASTINGAPPARATUS [72] Inventor: William E. Douglas, Birmingham, Mich.

[73] Assignee: General Motors Corporation, Detroit,

Mich.

[22] Filed: Dec. 14, 1970 [21] App1.No.: 97,850

[52] U.S.Cl ..164/312, 18/121 [51] Int. Cl ..B22d 17/04 [58] Field ofSearch ..18/5 BE, 5 B1, 30 EN, 30 FP,

18/30 QM, 30 QB,12 P; 164/47, 62,113,120-127, 136, 257, 284, 303, 306,309, 312, 313, 314, 316,

Primary Examiner-J. Spencer Overholser Assistant Examiner-John S. BrownAttorney-Peter P. Kozak and Sidney Carter [57] ABSTRACT Die castingapparatus of the horizontal cold chamber type operative to preventimpurities such as dross and metal foam floating on the surface of themolten metal charge in the shot sleeve from entering the die cavity. Theapparatus involves the elimination of the usual vertical runnerextending from the end of the shot sleeve adjacent the parting line ofthe dies to the die cavity, the provision of the overflow cavity aboveand at the end of the shot sleeve adjacent the parting line of the dies,and the provision of one or more runners extending from the lowerportions of the shot sleeve and around the overflow trap whereby whenthe plunger is caused to move the molten metal to the parting line ofthe die, the dross and metal foam formed on the surface of the die istrapped in the overflow trap and only clean metal is injected into thedie cavity.

4 Claims, 2 Drawing Figures PATENTED APR 2 5 m2 INVEN TOR. M71122!!! 530119105 DIE CASTING APPARATUS This invention relates to apparatus forforming metallic parts and in particular to pressure die castingapparatus. While the invention is broadly useful in the die casting artit is particularly applicable to die casting of light metals such asaluminum, magnesium and their alloys.

In the manufacture of metallic parts by pressure die casting it has longbeen recognized that extensive and sometimes prohibitive porosity willoccur in die castings. Significant advances in the art of die castinghave been made which materially reduce porosity as for example by thedie casting apparatus and method disclosed in the U.S. Pats. Nos.3,270,383 Hall et al. and 3,344,848 Hall et al. These patents disclose amethod and apparatus of a horizontal cold chamber type in which themolten metal is injected relatively slowly and nonturbulently into a diecavity from a shot sleeve located below the die cavity and whereby themolten metal is subjected to relatively high pressure after the diecavity is filled to avoid metal turbulence and to compact the moltenmetal within the cavity to substantially eliminate porosity.

It has been found that in the use of die casting apparatus of the typereferred to above wherein the runner is positioned in a vertical planeand leads directly from the top of the shot sleeve to the die cavity,the molten metal charge in the shot sleeve includes small amounts ofimpurities such as dross and metal foam on the surface thereof. When themolten metal is moved into the die cavity by means of the plunger thedross and metal foam are moved into the die cavity during the ejectionprocedure to produce imperfections in the cast article. Where it isdesired to cast articles such as internal combustion engine blocks evensuch minor imperfections are objectionable.

It is the basic object of this invention to provide die castingapparatus whereby the impurities such as dross and metal foam floatingon the surface of the molten metal in the shot sleeve is trapped duringthe casting cycle and not permitted to enter into the die cavity wherebysuch dross and metal foam as a source of casting porosity is effectivelyand efficiently eliminated.

It is a further object of this invention to provide relatively simpleand effective means whereby the aforementioned object is carried out bya relatively simple modification of existing die casting apparatus.

These and other objects are accomplished by the provision of die castingapparatus of the horizontal cold chamber type such as for example asdisclosed in the aforementioned patents which is modified to eliminatethe usual vertical runner extending from the end of the shot sleeveadjacent the parting line of the dies, to provide an enlarged spaced orenclosed overflow cavity at the end of the shot sleeve adjacent theparting line, and to provide one or more runners extending from thelower portions of the shot sleeve adjacent the parting line around theoverflow cavity and to the die cavity. In operation when the shot sleeveis filled with a charge of molten metal and the plunger is caused tomove the molten metal toward the parting line of the die the dross andmetal foam which are formed on the surface of the molten metal chargeare forced into the overflow trap and only clean molten metal is forcedfrom below the trap into the die cavity through the runners.

Other objects and advantages will be apparent from the followingdetailed description of this invention reference being made to thedrawings in which FIG. 1 is a vertical cross-sectional view through thedies and the shot sleeve of die casting apparatus with the dies in aclosed position and with the shot sleeve containing a molten metalcharge, and

FIG. 2 is a vertical cross-sectional view taken along line 2 2 of FIG.1.

Referring to the drawings FIG. 1 illustrates die casting apparatusincluding a cover die attached to a stationary platen l2 and an ejectordie 14 including a back plate 15 attached to a movable platen l6slidably mounted on the tie rods 18 in a manner well known in the art.The movable platen I6 is operative to move the ejector die 14 between adie closed position as shown in FIG. 1 to a die open position by meansof toggle links 20 attached to a toggle mechanism (not shown) which inturn is operated by hydraulic means (not shown) well known in the art.

The cover die 10 and ejector die 14 form a die cavity 22 therebetweenwhen in a closed position. The back plate 15 is removable to permitaccess to conventional ejector pin mechanism (not shown) containedwithin the ejector die 14 as is well known in the art.

The apparatus includes a shot sleeve 24 extending from outside thestationary platen 12 to the parting line 26 of the dies and having themolten metal charging port 25 and the shot plunger 27. The shot sleevewhich is usually of a cylindrical configuration includes the lowerhorizontal dimension 28 and the upper horizontal dimension 30. Thesedimensions refer to lower and uppermost horizontal, longitudinalinternal surfaces of the shot sleeve. The inner end of the shot sleeve24 adjacent the parting line 26 is provided with an enlarged portion oroverflow trap 32 extending vertically above the upper horizontaldimension 30 of the shot sleeve 24 as shown in FIGS. 1 and 2.

In accordance with this invention the usual vertical runner extendingfrom the shot sleeve to the die cavity is eliminated and the runners 34and 36 are provided adjacent the parting line 26 which preferablycommunicate between the die cavity 22 and the shot sleeve 24 from alocation as indicated at 38 in the vicinity of the lower horizontaldimension 28 of the shot sleeve and curve about the overflow trap 32. Itwill be readily apparent to those skilled in the art that this structuremay be readily incorporated in existing apparatus by suitably pluggingthe usual vertical runner as by welding and machining the overflow trapand new runners in the existing dies and shot sleeve.

It may readily be seen that when the shot sleeve 24 is provided with amolten metal charge 40 as shown in FIG. 1, the dross and metal foam willfloat on the surface 42 ofthe molten metal charge. When the plunger 27is actuated to inject the molten metal charge 40 into the die cavity 22the opening 25 of the shot sleeve the die closed and the molten metal iscarried forward toward the parting line of the dies with the dross andmetal foam floating on top thereof. As the plunger 27 proceeds the drossand foam are collected in the overflow cavity 32 and only clean moltenmetal is forced into the die cavity through runners 34 and 36respectively. When the plunger 27 reaches the limit of its travel asindicated by the broken line 46 and the molten metal is solidified, thebiscuit formed between the plunger 27 and the die 14 which includes thedross and metal foam solidified in the overflow cavity 32, is removedfrom the shot sleeve 24, the overflow cavity 32 and the runners 36 withthe casting when the dies are opened in a manner well known in the art.

It has been found that the volume of the overflow cavity 32 should be aminimum of 2 percent ofthe volume of the molten metal charge to insurethe entrapment of the dross and metal foam floating on the surface ofthe molten metal charge in the shot sleeve. A volume of bout 5 percentof the molten metal charge in most instances is an optimum to effectentrapment of the impurities referred to and to hold ofial down to aminimum.

While the invention has been shown in simplified form it is to beunderstood that the invention is particularly adapted to the casting ofarticles such as engine blocks in which case the runners 34 and 36 wouldinclude several branches extending to a plurality of gates at the diecavity to suitably fill the die cavity. Various modifications will beapparent to those skilled in the art in adapting this invention to thecasting of specific articles and to various die casting methods andapparatus.

It is claimed:

1. In a die casting apparatus the combination comprising a stationarycover die and a removable ejector die removable between a die openposition and a die closed position at a parting line cooperativelydefining a die cavity therebetween in said closed position,

a horizontally disposed shot sleeve having an uppermost and a lowermosthorizontal dimension and having one end thereof extending into saidcover die to said parting line, said shot sleeve having an enlargedportion adjacent said parting line extending upwardly above said upperdimension to form an enclosed overflow cavity,

said cover and said ejector dies defining at said parting line at leastone runner extending from a portion of said shot sleeve below saidoverflow cavity to said die cavity,

a shot plunger in said shot sleeve and an opening means in said shotsleeve for charging said shot sleeve with molten metal,

said overflow cavity, being operative to trap dross and metal foamfloating on the surface of a charge of molten metal in said shot sleeveand said runner being operative to convey clean molten metal from alocation below said overflow cavity when said plunger is operated tomove the molten metal into said die cavity.

2. The die casting apparatus of claim 1 wherein the volume of saidoverflow cavity is at least 2 percent of the volume of the molten metalcharge.

3. In a die casting apparatus the combination comprising a stationarycover die and a removable ejector die removable between a die openposition and a die closed position at a parting line cooperativelydefining a die cavity therebetween in said closed position,

a horizontal shot sleeve having an uppermost and a lowermost horizontaldimension disposed below said die cavity and having one end thereofextending into said cover die to said parting line, said shot sleevehaving an enlarged portion adjacent said parting line extending upwardlyabove said upper dimension to form an enclosed overflow cavity,

said cover and said ejector dies defining at said parting line at leastone runner extending from a portion of said shot sleeve in the vicinityof said lowermost horizontal dimension and below said overflow cavity tosaid die cavity,

a shot plunger in said shot sleeve and an opening means therein forcharging said shot sleeve with molten metal,

said overflow cavity the to trap dross and metal foam floating on t hesurface ofa charge of molten metal in said shot sleeve and said runnerbeing operative to convey clean molten metal from a location below saidoverflow cavity when said plunger is operated to move the molten metalinto said die cavity.

4. The die casting apparatus of claim 3 wherein the volume of saidoverflow cavity is at least 2 percent of the volume of said molten metalcharge.

t 1' i i EE-5&3? UNITED STATES PATENT bimibE" v CERTIFICATE CORRECTIONPatent No. 3,658 121 Dated April 1972 lnvenw i William E. Douglas It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 2,-line S7, "bout" should read about Claim 1, column 2, line 71,after 7 "a" delete "removable" and substitute movable column 2, line 71,after "die" delete "removable" and substitute Claim 3, column 3, line23, after "a" delete "removable" and substitute movable column 3, line23, after "die" delete "removable" and substitute movable I Column. 4,line 15, "the" should read being operative i signed and sealed this 12thday of September 1972-. (SEAL) 5 Attest: I

EDWARD M.FLETCHER,JR. I ROBERT GOTISCHALK Attesting Officer Commissionerof Patents

1. In a die casting apparatus the combination comprising a stationarycover die and a removable ejector die removable between a die openposition and a die closed position at a parting line cooperativelydefining a die cavity therebetween in said closed position, ahorizontally disposed shot sleeve having an uppermost and a lowermosthorizontal dimension and having one end thereof extending into saidcover die to said parting line, said shot sleeve having an enlargedportion adjacent said parting line extending upwardly above said upperdimension to form an enclosed overflow cavity, said cover and saidejector dies defining at said parting line at least one runner extendingfrom a portion of said shot sleeve below said overflow cavity to saiddie cavity, a shot plunger in said shot sleeve and an opening means insaid shot sleeve for charging said shot sleeve with molten metal, saidoverflow cavity being operative to trap dross and metal foam floating onthe surface of a charge of molten metal in said shot sleeve and saidrunner being operative to convey clean molten metal from a locationbelow said overflow cavity when said plunger is operated to move themolten metal into said die cavity.
 2. The die casting apparatus of claim1 wherein the volume of said overflow cavity is at least 2 percent ofthe volume of the molten metal charge.
 3. In a die casting apparatus thecombination comprising a stationary cover die and a removable ejectordie removable between a die open position and a die closed position at aparting line cooperatively defining a die cavity therebetween in saidclosed position, a horizontal shot sleeve having an uppermost and alowermost horizontal dimension disposed below said die cavity and havingone end thereof extending into said cover die to said parting line, saidshot sleeve having an enlarged portion adjacent said parting lineextending upwardly above said upper dimension to form an enclosedoverflow cavity, said cover and said ejector dies defining at saidparting line at least one runner extending from a portion of said shotsleeve in the vicinity of said lowermost horizontal dimension and belowsaid overflow cavity to said die cavity, a shot plunger in said shotsleeve and an opening means therein for charging said shot sleeve withmolten metal, said overflow cavity the to trap dross and metal foamfloating on t he surface of a charge of molten metal in said shot sleeveand said runner being operative To convey clean molten metal from alocation below said overflow cavity when said plunger is operated tomove the molten metal into said die cavity.
 4. The die casting apparatusof claim 3 wherein the volume of said overflow cavity is at least 2percent of the volume of said molten metal charge.